KR20070083710A - Electorlysis electrode and method for producing aqueous quaternary ammonium hydroxide solution using such electrolysis electrode - Google Patents

Abstract

Disclosed is an electrolysis electrode with excellent corrosion resistance and durability which can be used for a long time for producing high-purity quaternary ammonium hydroxide by electrolyzing an inorganic acid salt of quaternary ammonium in an electrolysis vessel using a cation exchange membrane as the diaphragm. In addition, this electrolysis electrode contributes to reduce power consumption, thereby enabling to commercially produce high-purity quaternary ammonium hydroxide at low cost. Specifically disclosed is electrolysis electrode which is used when quaternary ammonium hydroxide is produced by electrolyzing an inorganic acid salt of quaternary ammonium in an electrolysis vessel using a cation exchange membrane as the diaphragm. This electrolysis electrode is characterized in that an electrode base made of a conductive metal is coated with an electrode active layer containing an electrode active material, and an intermediate layer made of a mixed oxide composed of an oxide of at least one metal selected from the group consisting of In, Ir, Ta, Ti, Ru and Nb and an Sn oxide is arranged between the electrode base and the electrode active layer.

Description

ELECTROLYSIS ELECTRODE AND METHOD FOR PRODUCING AQUEOUS QUATERNARY AMMONIUM HYDROXIDE SOLUTION USING SUCH ELECTROLYSIS ELECTRODE}

The present invention relates to an electrolytic electrode used when producing quaternary ammonium hydroxide by electrolysis, and a method for producing a quaternary ammonium hydroxide aqueous solution which produces quaternary ammonium hydroxide by electrolysis using this electrolytic electrode as an anode. All.

Tetramethylammonium hydroxide (TMAH) aqueous solution, which is one of the quaternary ammonium hydroxides, is used for the development of a resist film used in the production of LSI, liquid crystal monitor, etc., the cleaning liquid of a semiconductor substrate in the manufacturing process of a semiconductor device, or tetramethylammonium silicate. It is currently used in large quantities as a compound, and is an essential compound industrially. In particular, when used for such a semiconductor-related use, the demand for impurity concentration contained in this TMAH is strict, for example, Na, K, Ca, Cu, Zn, Fe, Cr, Ni, Pb, Transition metals, alkali metals, alkaline earth metals and the like, including Ti and Sn, are required to have a purity of 1 ppb or less, respectively. Therefore, there is a demand for a method that can industrially produce a high purity TMAH aqueous solution at low cost.

The inventors of the present invention propose a method obtained by synthesizing an inorganic acid salt of quaternary ammonium by reacting trialkylamine and dialkyl carbonate as a method of producing TMAH, and electrolyzing this inorganic acid salt in an electrolytic cell using a cation exchange membrane as a diaphragm. There is (refer patent document 1). According to this method, halogen ions, formic acid ions, and the like, which cause corrosion of the electrode and deterioration of the exchange membrane during electrolysis, are not generated, and at the same time, high purity with few impurities as described above and excellent storage stability are also achieved. TMAH can be obtained, and also the yield can be raised.

In general, in the case of causing an electrode reaction in the electrolysis process, an insoluble electrode is used to avoid the consumption of the electrode itself. This insoluble electrode is classified into a chlorine generating electrode, an oxygen generating electrode, a functional electrode (platinum group metal coated electrode), etc. in that the performance required by the electrolytic product or the electrolytic object is different. In the method of producing the TMAH proposed by the present inventors, when the inorganic acid salt of the fourth ammonium is electrolyzed in an electrolytic cell using a cation exchange membrane as a diaphragm, oxygen and carbon dioxide gas are generated at the anode as shown in FIG. The pH of the inorganic acid salt of quaternary ammonium is about 8-10. Such electrolysis is not so much conventional.

In the electrolysis for producing such TMAH, an electrode made of gold (Au), platinum (Pt), silver (Ag), or the like, which is generally used as an electrode reaction in an electrolysis process as an anode, an electrode body made of graphite electrode, titanium When an electrode coated with a platinum group metal, a lead electrode, a Ni electrode, or an electrode coated with an oxide containing a platinum group metal as a main component is used, all have problems with corrosion resistance and durability, or electrolytic potential As the power consumption increases, power consumption increases, resulting in problems such as an increase in industrial costs. That is, for electrodes or graphite electrodes made of gold (Au), platinum (Pt), silver (Ag), or the like, the surface of the electrode is peeled off by electrolysis for several hours, the voltage rises, and it is difficult to continue the electrolysis. do. In addition, in an electrode in which a platinum group metal is plated on an electrode body made of titanium, expensive metals such as expensive Pt, Pd, and Ru are eluted in an order of ppm by electrolysis for several hours. On the other hand, an electrode coated with oxides of Ir and Ta as an electrode gas for titanium is for an electrolytic process that generates oxygen at the anode during electrolysis, and is used only for electroplating using a sulfuric acid bath. When used for electrolysis of an inorganic acid salt of quaternary ammonium which generates oxygen and carbon dioxide gas, oxygen and carbon dioxide gas are generated at the anode at the same time, the overvoltage in electrolysis is increased, durability of the electrode is lowered, and power consumption is increased. There is a problem such as throwing away. In general, lead electrodes, Ni electrodes, and graphite electrodes have a certain degree of durability and corrosion resistance as organic alkali electrodes as anode electrodes. However, in the electrolysis where oxygen and carbon dioxide are simultaneously generated at the anode, as in the electrolysis proposed by the present inventors, The electrode itself is extremely consumed and cannot be said to be an industrially satisfactory electrode.

By the way, in the electrode which coat | covered the electrode base which consists of a conductive metal with the electrode active material which consists of a platinum group metal or its oxide, oxide of one or more types of metals chosen from Ti and Sn and Ta between an electrode base and an electrode active material And an electrode provided with an intermediate layer made of a mixed oxide of an oxide of at least one metal selected from Nb (see Patent Document 2), or the intermediate layer comprising a first intermediate layer made of a rare earth metal compound and a nonmetal or nonmetal oxide. The electrode (refer patent document 3) formed from the intermediate | middle layer is also proposed. However, since both of these electrodes are for an electrolytic process in which oxygen is generated at the anode during electrolysis, when used for electrolysis of an inorganic acid salt of quaternary ammonium which generates oxygen and carbon dioxide gas at the anode, There is a problem in durability and corrosion resistance due to the increase in overvoltage, and there is a problem economically due to the increased power consumption.

Patent Document 1: Patent Publication No. 63-15355

Patent Document 2: Patent Publication No. 59-38394

Patent Document 3: Patent Publication No. 2-5830

Thus, the present inventors can reduce the elution of the impurity metal as much as possible while producing electrolytic quaternary ammonium hydroxide by electrolyzing an inorganic acid salt of quaternary ammonium in an electrolytic cell using a cation exchange membrane as a diaphragm, and excellent in corrosion resistance and durability. Furthermore, as a result of earnestly examining the electrolytic electrode which can reduce the power consumption and the overvoltage in electrolysis, an electrode active layer is further coat | covered with the mixed oxide of Sn oxide and the oxide of predetermined metal. The electrode coated with was found to be suitable for the electrolysis of the inorganic acid salt of quaternary ammonium as described above, and completed the present invention.

Accordingly, an object of the present invention is to produce a high-purity quaternary ammonium hydroxide by electrolysing an inorganic acid salt of quaternary ammonium in an electrolytic cell using a cation exchange membrane as a diaphragm, which is excellent in corrosion resistance and durability, and can be used for a long period of time. It is possible to provide an electrolytic electrode which can be reduced and can be produced in high purity without having to be industrially expensive.

Another object of the present invention is to provide a method for producing a quaternary ammonium hydroxide aqueous solution which can reduce the elution of impurity metal as much as possible and can produce high-purity quaternary ammonium hydroxide industrially at low cost.

That is, the present invention is an electrolytic electrode which is used to produce quaternary ammonium hydroxide by electrolysis of an inorganic acid salt of quaternary ammonium in an electrolytic cell using a cation exchange membrane as a diaphragm, and an electrode active layer made of a conductive metal includes an electrode active material. And an intermediate layer formed of a mixed oxide of an oxide of at least one metal selected from In, Ir, Ta, Ti, Ru, and Nb with an oxide of Sn between the electrode body and the electrode active layer. It is an electrolytic electrode characterized by the above-mentioned.

In addition, the present invention synthesizes an inorganic acid salt of quaternary ammonium by reacting trialkylamine with dialkyl carbonate, followed by electrolysis of the inorganic acid salt in an electrolytic cell in which an electrolytic electrode is used as an anode and a cation exchange membrane is used as a diaphragm. A method for producing an aqueous quaternary ammonium hydroxide, characterized by producing quaternary ammonium.

In the present invention, the method described in Japanese Patent Application Laid-Open No. 63-15355 is preferably used as a method for producing quaternary ammonium hydroxide by electrolysis of an inorganic acid salt of quaternary ammonium in an electrolytic cell using a cation exchange membrane as a diaphragm. That is, the inorganic acid salt of quaternary ammonium electrolyzed in the electrolytic cell using a cation exchange membrane as a diaphragm can be synthesized by reacting trialkylamine and dialkyl carbonate. Examples of the trialkyl amine include trimethylamine [(CH ₃ ) ₃ N] and triethylamine [(C ₂ H ₅ ) ₃ N]. Examples of the dialkyl carbonate include dimethyl carbonate [(CH ₃ ) ₂ CO ₃ ] And diethyl carbonate [(C ₂ H ₅ ) ₂ CO ₃ ], and the like, and these can be reacted in a solvent such as methyl alcohol or ethyl alcohol to synthesize a quaternary ammonium inorganic acid salt. About reaction conditions at this time, it can select suitably, For example, reaction temperature 100 degreeC-180 degreeC, reaction pressure 5-20 kg / cm <^2> , reaction time can be made into 1 hour or more. In addition, it is preferable to remove unreacted substances etc. by distillation or distillation under reduced pressure about the obtained reaction mixture after completion | finish of reaction. Thus, the inorganic acid salt of the quaternary ammonium synthesize | combined in this way can be represented by following General formula (1).

Here, in said general formula (1), R <^1> , R <^2> , R <^3> and R <^4> are a methyl group or an ethyl group, These may mutually be same or different.

In the above general formula (1), preferably a _{[(CH 3) 4 N]} HCO 3, [(C 2 H 5) 4 N] HCO 3.

When the quaternary ammonium inorganic acid salt is obtained, for example, in the above, trialkylamine and dialkyl carbonate are distilled and purified as described above, and the resulting reaction product is dissolved in water to provide an aqueous solution of the quaternary ammonium inorganic acid salt. The cation exchange membrane is supplied to the anode chamber of the electrolytic cell with a diaphragm, and electrolysis is performed by applying a DC voltage. As a result, the quaternary ammonium ions move to the anion chamber through the cation exchange membrane, and quaternary ammonium hydroxide is produced in the anion chamber. At this time, oxygen and carbon dioxide gas are generated at the anode, and hydrogen is generated at the cathode. As the cation exchange membrane, for example, a fluorocarbon exchange membrane excellent in durability as well as an inexpensive polystyrene or polypropylene exchange membrane can be used.

As for the positive electrode to be inserted into the electrolytic cell, the electrode for electrolysis in the present invention is used. That is, an electrode body made of a conductive metal is covered with an electrode active layer containing an electrode active material, and an oxide of at least one metal selected from In, Ir, Ta, Ti, Ru, and Nb between the electrode gas and the electrode active layer. Preferably, the electrolytic electrode provided with the intermediate | middle layer which consists of a mixed oxide of the oxide of Sn and the oxide of at least 1 sort (s) of metal chosen from In, Ir, and Ta is used. The intermediate layer of the electrolytic electrode is formed from a mixed oxide of an oxide of Sn and an oxide of at least one metal selected from In, Ir, Ta, Ti, Ru, and Nb, thereby increasing the oxide of Sn and other metal oxides. By the effect, it is possible to provide an electrode that exhibits excellent adhesion with the surface of the electrode body and is excellent in corrosion resistance and can withstand long-term electrolysis. Specific examples of the oxides of the metals selected from In, Ir, Ta, Ti, Ru, and Nb include In ₂ O ₃ , Ir ₂ O ₃ , IrO ₂ , Ta ₂ O ₅ , TiO ₂ , Ru ₂ O ₃ , NbO _2, and the like. that the there may be mentioned, it is preferably an in ₂ O _3, Ir ₂ O _3, and Ta ₂ O ₅ which is good, and more preferably that in ₂ O ₃ or Ir ₂ O ₃ in which exhibits excellent conductivity of the good. On the other hand, specifically an oxide of Sn as SnO and SnO ₂ may be mentioned, preferably a SnO _2. That is, in the present invention, the preferred mixed oxide forming the intermediate layer is preferably a mixed oxide of SnO ₂ with an oxide of at least one metal selected from In, Ir, Ta, Ti, Ru, and Nb as described above. specific examples of the _{in 2 O 3 -SnO 2, Ir} 2 O 3 -SnO 2, Ta 2 O 5 -SnO 2, in 2 0 3 -Ir 2 O 3 -SnO 2, in 2 O 3 -Ta 2 O 5 - _{SnO 2, Ir 2 O 3 -Ta} 2 O 5 -SnO 2, and _{In 2 O 3 -Ir 2 O 3} -Ta 2 O 5 and -Sn0 _2, and more preferably from _{In 2 O 3 -SnO 2, Ir} 2 O ₃ is _{-SnO 2, In 2 O 3 -Ir} 2 O 3 -SnO 2.

About the component ratio of the mixed oxide which forms an intermediate | middle layer, it is good that Sn content is 50-80 wt% in the genus (Sn) conversion amount, Preferably it is 60-70 wt%. If the content of Sn is less than 50 wt%, there may be a problem in terms of corrosion resistance and durability as the electrode, and if it is more than 80 wt%, the overvoltage when used as the electrode may be increased. Moreover, if it is the range of 60-70 wt%, it is preferable from a viewpoint of electroconductivity and the film strength formed by the characteristic of the mixed oxide with the oxide of metals other than Sn.

About the film thickness of the intermediate | middle layer in this invention, it is 3-100 micrometers, Preferably it is 10-40 micrometers. If the thickness of the intermediate layer is smaller than 3 mu m, pinholes are formed in the formed film, and the electrode gas is oxidized, thereby increasing the potential at the time of electrolysis, thereby making it difficult to flow current. On the contrary, when larger than 100 micrometers, there exists a possibility that a film strength may fall in the relationship of thermal expansion with an electrode body. Moreover, if it is 10-40 micrometers, it is preferable from a viewpoint of film strength, durability, and an electric current and a voltage. Moreover, about the intermediate | middle layer in this invention, it may be formed by the coating of one layer of mixed oxide, and may be formed by laminating | stacking two or more layers of mixed oxides.

As the electrode active layer containing the electroactive material in the present invention, for example, a platinum group metal such as Pt, Ru, Pd, Ir, a metal such as In or Sn, or an electrode active layer containing an oxide of these metals can be represented. It is excellent in adhesiveness and electroconductivity, and an electrode which consists of a mixed oxide of the oxide of Sn and the oxide of Sn at least 1 sort (s) preferably from Ir or In from a viewpoint of electrode potential and power consumption when used as an electrode. It is good to be an active layer. When the electrode active layer is made of a mixed oxide of an oxide of Sn and an oxide of at least one metal selected from Ir or In, specifically, the oxides of Ir and In include the same oxides as those described for the intermediate layer. SnO ₂ is similarly mentioned with respect to the oxide of Sn.

When the electrode active layer is made of a mixed oxide of at least one metal oxide selected from Ir or In and an oxide of Sn, the content of Sn is equal to the component ratio of the mixed oxide forming the electrode active layer. It is good that it is 50-80 wt% in terms of conversion amount, Preferably it is 60-70 wt%. If the Sn content is less than 50wt%, there may be a problem in terms of film strength and conductivity, and if it is more than 80wt%, the film strength may be weakened, and when used as an electrode, the voltage may be high and current may be difficult to flow. . When the Sn content is in the range of 60 to 70 wt%, it is particularly excellent in terms of the conductivity of the mixed oxide forming the electrode active layer and the film strength formed.

Moreover, about the film thickness of the electrode active layer in this invention, it is good that it is 3-40 micrometers, Preferably it is 5-20 micrometers. If the thickness of the electrode active layer is smaller than 3 µm, the thickness falls in terms of current characteristics. If the thickness of the electrode active layer is larger than 40 µm, the film strength may decrease in view of adhesion to the intermediate layer. Moreover, about the electrode active layer in this invention, it may be formed by the coating of one layer of mixed oxide containing an electrode active material, and may be formed by laminating | stacking the film which consists of two or more layers of mixed oxides.

Further, in the present invention, as the electrode base made of a conductive metal, for example, one metal selected from Ti, Ta, Nb, and Zr, or an alloy made of two or more kinds of alloys can be used. From the viewpoint of being easily available at low cost, Ti is preferable.

Although there is no restriction | limiting in particular about the method of manufacturing the electrode for electrolysis in this invention, For example, the following methods can be shown as an example.

First, the electrode base Ti, which is a conductive metal, is degreased with acetone or the like. Next, the surface of the electrode base is surface treated for about 5 to 30 minutes at a temperature of about 90 to 100 ° C. using hydrochloric acid having a predetermined concentration. After washing well with pure water. Meanwhile, a solution (mixed solution) in which chlorides of the metals of Sn (tin), Ir (iridium), and In (indium) are dissolved in alcohols such as butanol and propanol at a predetermined concentration, respectively, is prepared. It is applied to the surface of the electrode gas, and the electrode gas is first dried for about 30 to 60 minutes at a temperature of 80 to 100 ° C. in an air atmosphere, and then for about 10 to 30 minutes at a temperature of 450 to 500 ° C. in an air atmosphere. The solution is formed on the surface of the electrode body to form a film made of a mixed oxide of an oxide of Sn, an oxide of Ir, and an oxide of In. The process of forming the film of the mixed oxide is performed about 2 to 4 times in total, and an intermediate layer of about 3 to 30 µm can be provided on the surface of the electrode body.

When the first mixed oxide film forming the intermediate layer is formed on the surface of the electrode body, a chloride of Ta (tantalum) is dissolved in an alcohol such as butanol and propanol, and further added to the mixed solution to contain the chloride of Ta. The mixed solution may be applied to the surface of the electrode body to perform the above drying and pyrolysis treatments. As described above, the inclusion of Ta oxide in the film of the mixed oxide formed on the surface of the electrode gas for the first time can improve the adhesion with the electrode gas. Although the mixed solution containing the chloride of Ta may be used after the second time of the process of forming the film of the mixed oxide, the oxide of Ta (Ta ₂ O ₅ ) is inferior in conductivity, and preferably an intermediate layer is formed on the surface of the electrode body. It should be included only when installing the first mixed oxide film.

Next, a solution (mixed solution) in which chlorides of respective metals of Sn, Ir, and In are dissolved in alcohol such as butanol and propanol at a predetermined concentration is applied to the surface of the electrode gas provided with the intermediate layer, and the intermediate layer is formed. The same drying and pyrolysis treatment may be performed about 2 to 4 times in total to form a 5-20 μm thick electrode active layer, thereby obtaining an electrode for electrolysis in the present invention.

With respect to this electrode for electrolysis, if both the intermediate layer and the electrode active layer formed on the surface of the electrode body are referred to as a surface coating layer, the premixed oxide (mixing oxide forming the intermediate layer and the electrode active layer forming the intermediate layer) is formed. When the component ratio of the oxide) is expressed in terms of the metal equivalents contained in the mixed oxide, it is preferably 50 to 80 wt% of Sn, 10 to 30 wt% of Ir, 3 to 15 wt% of In, and 0.5 to 3 wt of Ta. It is good to contain in the ratio of%, Furthermore, it is preferable that Sn is 60-70 wt%, Ir is 10-20 wt%, In is 5-10 wt%, and Ta is 0.5-1.Owt%.

Among these, Sn has already been described. If Ir is less than 10 wt%, there is a problem in terms of conductivity and current value at the time of electrolysis, and if it is more than 30 wt%, there is a concern in terms of film strength of mixed oxides. When it is in the range of 10 to 20 wt%, it is more excellent in the relationship between current and voltage, which are electrical characteristics of the mixed oxide forming the surface coating layer. If In is less than 3 wt%, there is a problem in terms of conductivity and the voltage may increase, whereas if it is more than 15 wt%, the film strength of the mixed oxide may be lowered. If it is the range of 5-10 wt%, it is more excellent from a viewpoint of film strength, electroconductivity, durability, etc. If it is less than 0.5wt%, the synergistic effect on the adhesiveness with respect to an electrode body cannot be exhibited with respect to Ta, and when it exceeds 3wt%, a problem may arise in electroconductivity and the voltage at the time of electrolysis may increase.

Although the conditions for the electrolytic reaction at the time of producing a quaternary ammonium hydroxide by electrolysing the inorganic acid salt of a quaternary ammonium in the electrolytic cell which used the electrolytic electrode obtained above as a diaphragm with a cation exchange membrane can be selected suitably, for example, It can represent the conditions of the electrolysis reaction. That is, an aqueous solution of quaternary ammonium inorganic acid salt such as tetramethylammonium bicarbonate, tetramethylammonium carbonate, etc. is supplied to the anode chamber of the electrolytic cell so as to be in a range of 10 to 50 wt%, preferably 15 to 30 wt%. To supply. When supplying this pure water, it is preferable to use what added the appropriate amount (about 3-15 weight%) of quaternary ammonium hydroxide. The solutions in these anode chambers and cathode chambers are supplied in a circulating manner, and the current density is 8-20 A / dm ² , preferably in the range of 10-15 A / dm ² , and the residence time of each liquid in the anode chamber and cathode chamber is 10 to 60 seconds, preferably 20 to 40 seconds, and the electrolytic reaction is preferably performed until the concentration of quaternary ammonium hydroxide in the cathode chamber is 5-30 wt%, preferably 10-25 wt%. . The negative electrode inserted into the electrolytic cell is not particularly limited, but alkali resistant stainless steel, nickel or the like can be used.

[Effects of the Invention]

The electrolytic electrode in the present invention has an intermediate layer excellent in adhesion to the electrode body and is formed of a mixed oxide mainly composed of Sn oxide. When the inorganic acid salt of ammonium is used as the positive electrode for electrolysis, it is excellent in durability and corrosion resistance and can be used for a long time. In addition, the electrolytic electrode according to the present invention can reduce the overvoltage in the electrolysis process that generates oxygen and carbon dioxide gas during electrolysis, and can suppress power consumption. It is suitable for preparing tetraammonium. Further, when the electrolytic electrode is prepared by electrolysis of quaternary ammonium hydroxide as the anode, the elution of impurity metal is reduced as much as possible, and high-purity quaternary ammonium hydroxide can be industrially produced at low cost.

1 is a schematic explanatory diagram of an electrolysis process according to the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated more concretely based on an Example and a comparative example.

Example 1

[Production of Electrolytic Electrode]

A commercially available Ti plate having a thickness of 2.0 mm x 10 cm x 6 cm was degreased with acetone, and then immersed in a 20 wt% hydrochloric acid solution at 100 ° C. for 5 to 10 minutes for etching. Next, an aqueous solution of tin chloride containing 30 g / 100 ml of Sn and an aqueous solution of chloride (InCl ₃ ) containing 10 g / 100 ml of In was prepared, and both aqueous solutions were dissolved in butanol, and a total of 500 ml of a mixed solution was prepared. It was made. The mixed solution was applied to the surface of the electrode base, dried at 100 ° C. for 10 minutes in an air atmosphere, and further placed in an electric furnace maintained at 450 ° C. for 10 minutes of thermal decomposition under an air atmosphere. A series of four processes of coating, drying, and pyrolysis of the mixed solution were carried out four times in total to form an intermediate layer having a thickness of 6 탆 made of a mixed oxide on the surface of the electrode body. Only when first applied to the surface of the electrode body to dry and thermally decompose, an aqueous solution of chloride (TaCl ₅ ) containing 1.0 g / 100 ml of Ta is further added to the butanol solution and the aqueous solution of indium chloride. The mixed solution was used to dissolve to make a total of 500ml.

Next, an aqueous solution of tin chloride containing 20 g / 100 ml of Sn and an aqueous solution of chloride (IrCl ₃ ) containing 5 g / 100 ml of Ir are prepared, and both of these aqueous solutions are dissolved in butanol to be 500 m1, which is an electrode. The active material was applied to the surface of the electrode gas, dried at 100 ° C. for 10 minutes in an air atmosphere, and further placed in an electric furnace at 450 ° C. for thermal decomposition for 10 to 15 minutes under an air atmosphere. A series of four processes of coating, drying, and pyrolysis of the mixed solution were carried out in total four times, and an electrode active layer having a thickness of approximately 20 μm was formed on the surface of the intermediate layer to prepare an electrode for electrolysis.

In the above, when the electrolytic electrode is obtained, the metal component is measured using a fluorescent X-ray apparatus (SEA2210 manufactured by Shimadzu Co., Ltd.) at the time when the intermediate layer is formed on the surface of the electrode body, and included in the mixed oxide forming the intermediate layer. Oxide species and their ratios were obtained. At the time of forming the electrode active layer, the same measurement as described above was performed, and the oxide species contained in the mixed oxide forming the electrode active layer and the ratio thereof were determined. Each result is shown in Table 1.

In addition, for the electrolytic electrode, a mixed oxide (intermediate layer forming an intermediate layer and an electrode active layer. The intermediate layer and the electrode active layer may be referred to as "surface coating layer" may be sometimes referred to as "surface coating layer"). The composition of the mixed oxide and the mixed oxide forming the electrode active layer) were determined by the above-mentioned fluorescent X-ray apparatus. Table 2 shows the results of expressing the metal content contained in the mixed oxide forming the surface coating layer in terms of metal.

[Electrolysis Using Electrodes for Electrolysis]

A cation exchange membrane (trade name: Nafion (registered trademark) manufactured by DuPont) -324 is used as a cathode using a commercially available Ni plate having a thickness of 2.0 mm x 10 cm x 6 cm as a cathode, using the electrolytic electrode obtained as described above. One tank type electrolytic cell arrange | positioned as a diaphragm was prepared. 7 liters of 30 wt% aqueous tetramethylammonium bicarbonate solution was placed in the anode chamber of this electrolyzer, and 1 liter of 3 wt% tetramethylammonium hydroxide (TMAH) solution was added to the cathode chamber, and these aqueous solutions were continuously pumped. While circulating, electrolysis was performed for 600 hours under the condition of a voltage of 8 V, a current of 1.7 A, and an effective electrolyte area of 16 cm ² of the cation exchange membrane, and 5.3 kg of 25 wt% TMAH was obtained on the cathode side. After electrolysis, the aqueous solution in the positive electrode chamber was 2.3 liters of an aqueous 5.1 wt% tetramethylammonium bicarbonate solution.

When the external appearance of the electrode for electrolysis (anode) after electrolysis was observed visually, the change was not recognized especially about the positive electrode itself and the aqueous solution in a positive electrode chamber. In addition, there was no change in the weight of the electrolytic electrode (anode) measured before the start of electrolysis and the result of the weighing after electrolysis for 600 hours. Electrolysis was carried out using the electrolytic electrode (anode) again under the above conditions, and electrolysis was carried out three times in total (600 hours x 3 = 1800 hours), and the appearance observation (anode itself and aqueous solution in the anode chamber) and weighing were performed. In particular, no change was recognized (Table 2). The metal impurities in the aqueous solution in the anode chamber and the cathode chamber after electrolysis were analyzed by atomic absorption spectrometer (Varian Co., Ltd.), respectively, and the metal impurities eluted in each solution were obtained. The analysis value of the aqueous solution in a positive electrode chamber is shown in Table 3, and the analysis value of the aqueous solution (TMAH) in a negative electrode chamber is shown in Table 4, respectively.

Example 2

An electrode for electrolysis was prepared in the same manner as in Example 1 so that the oxide species contained in each mixed oxide forming the intermediate layer of the electrolytic electrode and the electrode active layer and the ratio thereof were the same as in Table 1. For the mixed solution, when the intermediate layer is formed, an aqueous solution of tin chloride containing 30 g / 100 ml Sn and an aqueous solution of chloride (InCl ₃ ) containing 3 g / 100 ml In is dissolved in butanol to make 500 ml in total. When forming the electroactive layer, an aqueous solution of tin chloride containing 32 g / 100 ml Sn and an aqueous solution of chloride (IrCl ₃ ) containing 5 g / 100 ml Ir were dissolved in butanol to 500 ml in total. In addition, the obtained electrolytic electrode was measured using the fluorescent X-ray apparatus similarly to Example 1 (Table 1). In addition, the aqueous solution of the chloride containing Ta used in Example 1 at the time of forming an intermediate | middle layer did not use in Example 2, and formed the intermediate | middle layer.

Using the obtained electrolytic electrode as an anode, it carried out for 600 hours similarly to Example 1 (Table 2). As a result of visually observing the appearance of the electrode for electrolysis (anode) after electrolysis, the change in the anode itself and the aqueous solution in the anode chamber was not particularly recognized, and the weight change of the electrode for electrolysis (anode) before and after electrolysis Was also not recognized. Furthermore, in the same manner as in Example 1, the change was not particularly recognized in terms of appearance observation (anode itself and aqueous solution in the anode chamber) and weight change after electrolysis three times in total (Table 2). The metal impurities in the aqueous solution in the anode chamber and the cathode chamber after electrolysis were analyzed in the same manner as in Example 1 using an atomic absorption spectrometer, and metal impurities eluted in each solution were obtained. The analysis value of the aqueous solution in a positive electrode chamber is shown in Table 3, and the analysis value of the aqueous solution (TMAH) in a negative electrode chamber is shown in Table 4, respectively.

Comparative Example 1

In the same manner as in Example 1, a commercially available Ti plate was prepared and subjected to etching treatment. An aqueous solution of chloride (IrCl ₃ ) containing 15 g / 100 ml of Ir and a chloride (TaCl ₅ ) containing 5 g / 100 ml of Ta was prepared, and both of these aqueous solutions were dissolved in butanol to prepare a 500 ml mixed solution. It was made. This mixed solution is applied to the surface of the electrode gas, and a series of treatments for drying and pyrolysis are carried out five times in total under the same conditions as in Example 1, and a film layer having a thickness of approximately 10 μm is formed on the surface of the electrode gas. Produced.

Electrolysis was carried out for 100 hours in the same manner as in Example 1, except that the electrode according to Comparative Example 1 was used as the anode, using the same electrolytic cell as in Example 1.

In the same manner as in Example 1, when the external appearance of the electrolytic electrode (anode) after electrolysis was observed visually, it was recognized that the surface of the anode turned white and part of the Ti plate was exposed, and the aqueous solution in the anode chamber was also observed. It was confirmed that it was colored blue. In addition, the weight of the positive electrode after electrolysis was reduced by about 0.02 g compared with before electrolysis. In addition, the electrolytic voltage after 100 hours had risen by 1 to 2V since the start of electrolysis (Table 2). The metal impurities of the aqueous solution in the anode chamber and the cathode chamber after electrolysis were analyzed in the same manner as in Example 1, and the analysis values of the aqueous solution in the anode chamber were shown in Table 3, and the analysis values of the aqueous solution in the cathode chamber were shown in Table 4.

Comparative Example 2

In the same manner as in Example 1, a commercially available Ti plate was prepared and subjected to etching treatment. An ordinary plating treatment was performed on the surface of the Ti plate to form a platinum plated film having a thickness of 0.1 탆 to form an electrode. Electrolysis was carried out for 100 hours in the same manner as in Example 1, except that the electrode according to Comparative Example 2 was used as the anode, using the same electrolytic cell as in Example 1. In the same manner as in Example 1, when the external appearance of the electrolytic electrode (anode) after electrolysis was observed visually, no change was observed in the positive electrode itself and the aqueous solution in the positive electrode chamber, but elution of Pt was confirmed for about 5 hours at the start of electrolysis. (50 ppb elution after electrolysis) The weight of the positive electrode after electrolysis was reduced by 0.02 g compared to before electrolysis. In addition, the electrolytic voltage after 100 hours had risen 6 to 10V since the start of electrolysis (Table 2). The metal impurity of the aqueous solution in the anode chamber and the cathode chamber after the electrolysis was analyzed in the same manner as in Example 1, the analysis values of the aqueous solution in the anode chamber are shown in Table 3, and the analysis values of the aqueous solution in the cathode chamber are shown in Table 4.

Comparative Example 3

In the same manner as in Example 1, a commercially available Ti plate was prepared and subjected to etching treatment, and the plating was performed on the surface of the Ti plate by a conventional plating process to form a plated film having a thickness of 0.1 mu m to form an electrode. The electrolysis was carried out in the same manner as in Example 1, except that the electrode according to Comparative Example 3 was used as the anode, using the same electrolytic cell as in Example 1. A little after the start of the electrolysis, the plated film of the anode began to peel off, and in about 10 minutes, the gold plated film almost completely peeled off, so that subsequent electrolysis was stopped. At this point in time, the metallic impurities in the aqueous solution in the anode chamber and the cathode chamber were analyzed in the same manner as in Example 1, the analysis values of the aqueous solution in the anode chamber are shown in Table 3, and the analysis values of the aqueous solution in the cathode chamber are shown in Table 4. Moreover, about the aqueous solution of an anode chamber, since the gold-plated film peeled, it could not be measured.

[Comparative Example 4]

A high-purity (purity 99.9%) carbon plate was prepared in a size of 10 mm thick x 10 cm wide x 6 cm wide, and this was etched twice with 90 wt% hydrochloric acid at 90 ° C to obtain an electrode. Except for using the electrode of the carbon plate of this comparative example 4 for the positive electrode, electrolysis was performed for 500 hours in the same manner as in Example 1 for the aqueous solution supplied to the positive electrode chamber and the negative electrode chamber. .

After electrolysis, the aqueous solution in the anode chamber became black and the anode thickness was consumed from 10 mm to 7 mm before electrolysis (Table 2). The metal impurities of the aqueous solution in the anode chamber and the cathode chamber after electrolysis were analyzed in the same manner as in Example 1, and the analysis values of the aqueous solution in the anode chamber were shown in Table 3, and the analysis values of the aqueous solution in the cathode chamber were shown in Table 4. In addition, about the aqueous solution of the positive electrode chamber, consumption of the positive electrode was severe and measurement was not carried out.

The electrolytic electrode in the present invention is an electrode excellent in durability and corrosion resistance because it has an intermediate layer excellent in adhesion to the electrode body, and the intermediate layer is formed of a mixed oxide mainly composed of Sn oxide. It can be used for a long time as an anode when electrolytic acid of a quaternary ammonium is electrolyzed in the membrane-forming electrolytic cell. In addition, when the electrolytic electrode according to the present invention is used, the overvoltage can be lowered in the electrolysis process that generates oxygen and carbon dioxide gas during electrolysis, so that power consumption can be suppressed. Quaternary ammonium hydroxide can be prepared. The quaternary ammonium hydroxide obtained in this way is suitable as a processing agent for cleaning a developer, a semiconductor substrate (wafer), etc. used in the manufacture of LSI, a liquid crystal monitor, and the like.

Claims (7)

An electrolytic electrode used to produce quaternary ammonium hydroxide by electrolysis of an inorganic acid salt of quaternary ammonium in an electrolytic cell using a cation exchange membrane as a diaphragm. The electrode body made of a conductive metal is an electrode active layer containing an electrode active material. And an intermediate layer formed of a mixed oxide of an oxide of at least one metal selected from In, Ir, Ta, Ti, Ru, and Nb with an oxide of Sn between the electrode body and the electrode active layer. Electrolytic electrode made into. The electrolytic electrode according to claim 1, wherein the intermediate layer is a mixed oxide of an oxide of at least one metal selected from In, Ir, and Ta and an oxide of Sn. The electrolytic electrode according to claim 1, wherein the electrode active layer is a mixed oxide of an oxide of Sn and an oxide of at least one metal selected from In or Ir. The electrolytic electrode according to any one of claims 1 to 3, wherein the electrode body is made of one or two or more alloys selected from Ti, Ta, Nb, and Zr. The electrolytic electrode according to any one of claims 1 to 4, wherein the inorganic acid salt of the fourth ammonium is a compound represented by the following general formula (1).

In which R ^l , R ² , and R ³ And R ⁴ is a methyl group or an ethyl group, which may be the same as or different from each other) The electrode for electrolysis according to any one of claims 1 to 5, wherein the quaternary ammonium hydroxide is tetramethylammonium hydroxide. Trialkylamine and dialkyl carbonate were reacted to synthesize an inorganic acid salt of quaternary ammonium. Then, the electrolytic electrode according to any one of claims 1 to 6 was used as an anode and a cation exchange membrane was used as a diaphragm. A method for producing a quaternary ammonium hydroxide aqueous solution, wherein the inorganic acid salt is electrolyzed in an electrolytic cell to produce quaternary ammonium hydroxide.

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